Apparatus for straightening elongated members

ABSTRACT

Tubular members, such as sections of tubing for use in millimeter waveguide systems, are straightened through the use of roller or rotary straightener apparatus. The previously common creation of helical indentations along the inner walls of the tubular members, which has been found to result from a discontinuous surface contact at discrete points between the tubular members and conventional straightening rollers, is avoided by the use of special-purpose rollers. The specialpurpose rollers are shaped such that the tubular members undergoing straightening maintain intimate surface contact with the rollers throughout a continuous contact path extending along a substantial length of the surface of each roller. Each special-purpose roller may be formed by positioning a cylindrical cutting tool, of a diameter equal to that of a tubular member to be roller straightened, at a selected acute angle to the axis of a roller blank and in contact with the roller blank, and then rotating both the cutting tool and the roller blank. Subsequent roller straightening will take place with each tubular member oriented at the selected acute angle to the finished roller. Alternatively, a mathematical analysis may be employed to characterize the required roller shape. Numerically controlled machining techniques may then be utilized to form the specialpurpose rollers in accordance with the determined shape.

United States Patent [1 1 Lilienthal, 11 et al APPARATUS FORSTRAIGHTENING ELONGATED MEMBERS [75] Inventors: Peter FrederickLilienthal, 11,

Princeton; Karapurath Remachandran; Edward Stephen Tice, both ofl-lightstown, all of NJ.

[73] Assignee: Western Electric Company,

Incorporated, New York, NY.

[22] Filed: Dec. 16, 1971 [21] Appl. No.: 208,849

Primary Examiner-Milton S. Mehr v ifl zgyzlaqk 9JLEIPB [4 Dec. 25, 1973[57 ABSTRACT Tubular members, such as sections of tubing for use inmillimeter waveguide systems, are straightened through the use of rolleror rotary straightener apparatus. The previously common creation ofhelical indentations along the inner walls of the tubular members, whichhas been found to result from a discontinuous surface contact atdiscrete points between the tubular members and conventionalstraightening rollers, is avoided by the use of special-purpose rollers.The special-purpose rollers are shaped such that the tubular membersundergoing straightening maintain intimate surface contact with therollers throughout a continuous contact path extending along asubstantial length of the surface of each roller.

Alternatively, a mathematical analysis may be employed to characterizethe required roller shape. Numerically controlled machining techniquesmay then be utilized to form the special-purpose rollers in accordancewith the determined shape.

2 Claims,'6 Drawing Figures PATENTEDDECESIBIS 3. 780.558

- sum 10F 2 PRIOR ART APPARATUS FOR STRAIGHTENING ELONGATED MEMBERSBACKGROUND OF THE INVENTION This invention relates to methods ofstraightening an elongated member and, more particularly, to methods ofstraightening a tubular member wherein the creation of localizeddeformations along the inner wall of the tubular member due to thestraightening operation is substantially avoided.

In the art of manufacturing tubing, it is known to shape a blank intotubular form, for example, by deforming a flat, rolled metal strip andseam welding the deformed strip; to dimension the shaped tubing to adesired sized, for example, by drawing operations utilizing an externaldie and an internal mandrel; and to straighten the shaped anddimensioned tubing, typically through the use of conventional rotarystraightening or roller straightening apparatus.

Roller straightening apparatus generally employed in the manufacture oftubing includes a number of rollers, for example, three pairs ofrollers, which simultaneously rotate, axially advance and apply plasticbending stresses to sections of tubing undergoing straighteningoperations. A central pair of rollers is displaced laterally from a linejoining the two other pairs to apply the plastic bending stresses to thetubing. The roller pairs squeeze and turn the tubing to provide therotation and axial advance. The application of plastic bending stressesto a rotating section of tubing of imperfect straightness advancingthrough the rollers causes the section to spring back elastically into astraighter configuration after plastic deformation has taken placewithin the roller straightener apparatus. A number of passes through theapparatus may be employed to reduce the axial curvature of the sectionof tubing to an acceptable level.

Conventional roller straightener apparatus is adapted to performstraightening "operations on tubing sections having a wide range ofouter diameters. As a result, the general purpose rollers employed insuch apparatus are contoured to provide an acceptable degree of surfacecontact with many different sizes of tubing. In order to rollerstraighten a section of tubing of any particular outer diameter, thetubular section is simply placed between the rollers of each roller pairand the rollers are pressed toward one another and maneuvered angularlyuntil the apparent best fit between the contours of the roller and thesurface of the section of tubing is achieved. Roller straightening thentakes place, while roller pressure is maintained on the tubing.

With particular reference, now, to the art of manufacturing tubularmembers to be used as sections of waveguide tubing for transmittingwaves of millimeter wavelength, a high degree of perfection instraightness must be combined with a high degree of smoothness anduniformity of the inner wall of a tubular member to provide anacceptable product. It has been found that conventional rollerstraightening apparatus, using the available general purpose rollers,has not been capable of producing straightened tubular members suitablefor utilization in millimeter waveguide systems. Subsequent to thestraightening of tubularmembers to an acceptable straightness conditionutilizing the available rollers, helical indentations have been observedalong the inner walls of the members. These helical indentations havebeen found to result from a failure of the rollers and the tubularmembers to mate perfectly at their surfaces during the straighteningoperation. Instead, one or more individual contact points are present,forming regions of highly concentrated stress application on the surfaceof the tubular members which result in the internal helicalindentations. These deformities, being periodic in nature, ordinarilyrender the tubular members unacceptable for use as millimeter waveguidesections.

It has been determined that a continuous contact path, rather thancontact at one or more points, between the roller and tubular membersurfaces is necessary to assure the elimination of the undesirablehelical indentations. The suggestion has been made that the continuouscontact path condition might be achieved by utilizing rollers havinghyperbolic contours. Analysis has proved, however, that a hyperbolicallyshaped roller will not provide a perfect mate between the roller andtubular member surfaces along a substantial axial length of the roller.

Clearly, it would be most advantageous in the manufacture ofhigh-quality tubular members, such as for use in millimeter waveguidesystems, to provide methods of roller straightening sections of tubingwithout forming helical indentations along the inner walls of thetubing, for example, through the manufacture and utilization ofspecially designed rollers achieving a continuous contact path with thetubing sections undergoing straightening. No such rollers are presentlyavailable in the art, nor is any method for their design and manufacturegenerally known.

SUMMARY OF THE INVENTION An object of the invention resides in new andimproved methods of straightening an elongated member, such as methodsof straightening a tubular member whereby the creation of localizeddeformations along the inner wall of the tubular member due to thestraightening operation is substantially avoided.

The invention contemplates the provision of a set of specially contouredrollers for straightening tubular members of a given outer diameter.Each roller has a surface configured such that a tubular member and theroller will engage each other during the straightening operationthroughout a continuous contact path extending along a substantiallength of the roller. It has been found that by utilizing straighteningapparatus having rollers of this type, it is possible to produce tubularmembers of a high degree of straightness which do not exhibit theinternal helical deformities characteristic of prior art methods.

One method for producing rollers having surface contours configured toprovide the desired continuous contact path, in accordance with theprinciples of the invention, involvesthe use of a cylindrical cuttingtool with an outer diameter equal to the given outer diameter of tubularmembers to be roller straightened. A roller blank is machined with thecutting tool by rotating both the tool and the blank while the toolengages the blank at an acute angle to the axis of the blank. Subsequentroller straightening operations will be performed with the same acuteangle maintained between each tubular member to be. straightened and thefinished roller.

An alternative method for forming rollers of the desired configurationinvolves a mathematical analysis for characterizing the required shapeof each completed roller. Numerically controlled machining techniquesmay be thereafter employed to manufacture the rollers in accordance withthe determined shape.

BRIEF DESCRIPTION OF THE DRAWING.

FIG. 1 of the drawing is an isometric view of conventional rollerstraightening apparatus, well known in the prior art;

FIG. 2 is an isometric view illustrating a method of forming a roller inaccordance with the principles of the invention, the roller beingadapted for use in the prior art apparatus of FIG. 1 in order to providea continuous contact path, along a substantial length of the roller,with a tubular member to be straightened by the apparatus;

FIG. 3 is an isometric view of a model roller and tubular memberstructure, useful in analyzing the roller surface configuration requiredto provide a continuous contact path, along a substantial length of theroller, with a tubular member to be straightened;

FIG. 4 is a cross sectional view of the roller and tubular member ofFIG. 3 along a plane parallel to an X-Y plane depicted in FIG. 3; and

FIGS. 5 and 6 are elevational views of the roller and tubular member ofFIG. 3, taken looking along a Y axis and an X axis, respectively, asdefined in FIG. 3

DETAILED DESCRIPTION Referring to FIG. 1 of the drawing, conventionalroller straightening apparatus 10, well known in the prior art, isdepicted. The apparatus, which may be employed to straighten anelongated rod or tubular member 11, includes a number of angularlydisposed rollers 12. The rollers are grouped in pairs A, B, C, with oneroller of each pair positioned opposite the other roller of the pair.Provision is made for relative motion between the rollers of each pairsuch that a tubular member, having any of a number of different possibleouter diameters, may be inserted between the rollers and the rollersmoved relatively together and/or angularly to grip the tubular member.

During the straightening of a bent tubular member, the end pairs ofrollers A and C are typically disposed substantially in alignment witheach other, with the central pair B offset, e.g., vertically, from theline joining the roller pairs A and C. Driven rotation of one or more ofthe rollers 12, typically driven rotation of all of the rollers, causesthe bent tubular member 11 to rotate and to advance in the directionfrom roller pair A to roller pair C. As a section of the rotatingtubular member passes from roller pair A to roller pair B, the sectionis subjected to bending stresses beyond the elastic limit of the tubingmaterial. The plastic deformation which occurs in the vicinity of thecentral pair of rollers B during continued rotation of the tubularmember is such as to cause the deformed section to spring backelastically into a straighter configuration than that previously presentas the section passes from roller pair 8 to roller pair C.

Due to the fact that the prior art apparatus 10 is intended for use instraightening tubular members of various sizes, the rollers 12 of thepairs A, B, C are designed for gripping engagement with tubes having awide range of outer diameters. When straightening a tubular member ofany particular diameter, the general purpose rollers 12 of each pair A,B, and C are brought together and maneuvered angularly until an apparentbest fit with the surface of the tubular member is obtained, and theroller straightening operation is then begun.

It has been observed that a helical deformation is present along aninner wall of tubular members straightened by conventional rollerstraightening apparatus such as that shown in FIG. 1. These helicaldeformations, which are of sufficient magnitude to render the tubularmembers unsuitable for use as sections of millimeter waveguide tubing,have been found to result from the presence of a single point of contactor a discontinuous plural point contact between the general purposerollers 12 and each successive tubular member 11 undergoingstraightening. Elimination of the internal helical deformation can beassured only through the presence of a continuous, intimate surfacecontact between a tubular member being straightened and a substantiallength of each straightening roller 12, a condition which cannot beachieved utilizing the rollers of the prior art apparatus 10.

Turning now to FIG. 2 of the drawing, there is illustrated a method offorming rollers for use in roller straightening apparatus, which rollerswill provide the desired continuous contact path between the roller andtubular member surfaces during straightening. A cylindrical cutting tool21 has an outer diameter equal to the outer diameter of a number oftubular members subsequently to be straightened through the use of aroller formed from a blank 22. The cutting tool is brought intoengagement with the surface of the blank with the axis of the toolmaintained at an acute angle 6 to the axis of the blank. The cuttingtool 21 and the roller blank 22 are then rotated about their respectiveaxes such that a recessed area 23 is cut into the blank. A finishedroller is produced which will maintain intimate contact over asubstantial, continuous length of the roller with a tubular member ofthe same diameter as that of the cutting tool 21 when the tubular.member is placed within the recessed area 23 oriented at the acute angle8 with respect to the finished roller. A different set of rollers may befabricated for each particular size of tubular member to bestraightened.

An alternative method is also available for forming rollers configuredto provide an elongated, continuous path of contact with a tubularmember. The alternative method involves a mathematical analysis of thecontact between a roller, such as that produced by the methodillustrated in FIG. 2, and a tubular member undergoing rollerstraightening.

With particular reference to FIG. 3 of the drawing, an imaginary centralcutting plane 30 is passed through an elongated, continuous path ofcontact between a section of a tubular member 31 and a roller 32 havingthe desired surface configuration. The plane 30 intersects the rolleraxis perpendicularly at the longitudinal center of the roller. For easein analysis, the section of the tubular member is treated as essentiallystraight. This approximation has been found experimentally to be quitesound, in that rollers produced according to the analytical methodexhibit the desired elongated, continuous contact path with tubularmembers to be straightened, and in that such rollers permitstraightening to occur without the production of objectionable helicalindentations along the inner walls of the tubular members.

Three mutually perpendicular axes are illustrated in FIG. 3. A Z axis iscoincident with the axis of the roller, while an X axis and a Y axis liealong the plane 30. The Y axis is selected such that the axis of thetubular member 31 is parallel to a plane which includes the Y and Zaxes. FIGS. 5 and 6 show the engaged tubular member 31 and roller 32,looking, respectively, along the Y and Xaxes. The cross-sectionalconfigurations 41, of the tubular member 31, and 42, of the roller 32,along another imaginary cutting plane 40 perpendicularly intersectingthe Z axis at an arbitrary distance 10 from the X-Y plane 30, aredepicted isometrically in FIG. 3 and looking along the Z axis in FIG. 4.

An examination of FIG. 4 reveals that the tubular member 31 of FIG. 3displays an elliptical cross section 41 in the imaginary cutting plane40. The center of the ellipse is assigned the coordinates x,,, Y andz,,. The roller 32 has a circular cross section 42 in the plane 40. Theradius R is to be determined. A set of radius values for the rollercorresponding to a sufficiently large set of imaginary cutting planespassed through the roller, perpendicularly to the axis of the roller, atvarying positions along the roller axis will, of course, define thesurface contour of the roller to such a degree that the roller may beproduced by conventional methods of numerically controlled machining.

Since the axis of the tubular member 31 is parallel to the Y -Z plane(see FIG.

X0 R1 R2 where R is the radius of the tube 31 and R, is the radius ofthe cross section of the roller 32 in the central cutting plane 30 (seealso FIG. 3).

Also (See FIGS. 3 and 6),

y z,,/tan 0 The equation of the circular cross section 42 (FIGS.

3 and 4) of the roller 32 in the cutting plane 40 at the height 2 is ouspath of contact between the tubular member 31 and the roller 32. Thus,

Ha rs}? 329$ 41 /y o) (y y. 1

(6) 5 which may be solved for x, yielding x oy ""]/[y( yo l Bysubstituting Equation (7) into Equation (4), the

equation for the elliptical cross section 41 (FIG. 4), and rearrangingterms,

iffiy' i W b2 a which can be expressed, as will be shown hereafter, inthe more useful form Ay+By +Cy +Dy+E=0 25 where A cot 0 B= 2y,,(cot 0-cot 0) C x lsin 0 y,, 4y cot 0+y,, cot0- (R cot 0/sin 0 D 2x,, y /sin 02y, 2y,, cot 0 2R y cot filsin 0) E ("0 3 1) l yo l yo The derivation ofEquation (9) from Equation (8) proceeds as follows. Equation (8),

X02112 [(y '..)/(y( a yn l y.) l 1 may be rewritten as (y-y.){ x3 /y(b-a )+y,,a] +1/b 1 40 (W.){ o +[y( a)+yo l i ly( --a M 1 yielding (y2yaY+yo)[ +y -4 yoy +yo l [y a yoy -a )+yo (12) Since a R and b R lsin0,

R 4 R 2 2 (y yuy+yo +1 (fi 1 R 2 y 1 1 )+I /o 1 2 2 )2 sin 0 (sin 0 R12R 2 R12 R z 2 4 5 l s 0' 1 1/0 I yay (5 -1) +110 2 sin 6 11 210 cot? a)19+ (w) it 89 sin 0 1 1 4 +(1 /o 0 cot (9)11 (2 sinz 31 cot 6 y (sin 91102) 0 By collecting terms, Equation (16) can be rewritten in the formof Equation (9 as follows: [cottl] y [2y,,cot 02y,,cot0] y [xf/sinHy,4y,, cot0-l-y, cot0-R, lsinf) cotG] The three coordinates, x, y, z,,,at the point of tangency 44 are now known. The radius R may be foundfrom Equation (3), the equation of the circular cross section,rearranged. as follows:

i flaw a This procedure can be repeated for many selected values of z inorder to characterize the shape of a roller 32 which will providemaximum contact with a tube 31 of a given diameter (2R disposed at thedesired angle of orientation 6 with respect to the roller of a givenminimum radius R For the purpose of simplifying the forming of a rollerhaving a shape determined in the manner just described, it is preferredto utilize conventional computer equipment. A computer is programmed, inaccordance with standard programming techniques, to provide a set ofradius values, R, corresponding to a series of incrementally spacedpoints along the axis of the roller, i.e., the Z axis, for a tubularmember of each given outer diameter of interest. A number of numericalcontrol tapes, one for each given tubular member diameter to be rollerstraightened, may be generated from the set of radius values so derived.The tapes may be employed in known manner to manufacture the desiredrollers with commercially available, numerically controlled machiningapparatus. Alternatively, templates may be generated, the templateshaving contours from which rollers may be formed by using commercialtracing apparatus such as a tracer lathe or a tracer grinder.

The length of the path of contact P (FIG. 5) between a tubular memberand a roller so formed can be determined by computing the distancebetween any two successive points of tangency and summing the computeddistances from the midpoint of the roller surface, x R y 0, z 0, to thelast investigated point, x, y, 2, using the equation for the distance8,, 2% between any two adjacent points 1 and 2,

Sets of rollers, formed by numerically controlled machining apparatus asindicated above, have been employed in straightening tubular members ofvarying outer diameters, utilizing commercially available rollerstraightening apparatus of the type depicted in F IG. 1 of the drawing.The rollers of each set were oriented in pairs, in the manner shown inFIG. 1, defining a path of travel interconnecting the pairs of rollersalong the central axis of each roller pair. Each roller was disposedtangentially to the path of travel at the previously selected acuteangle 0, thereby forming the acute angle 6 with each successive tubularmember advanced along the path of travel during straightening. Thetubular members were observed to exhibit intimate contact with thesurfaces of the rollers throughout a continuous contact path extendingalong a substantial length of the roller surfaces. Moreover, thestraightened tubular members were characterized by a very high degree ofstraightness without any formation of undesirable helical deformationsalong the inner walls of the member.

it is to be understood that the above-described methods are simplyillustrative of certain embodiments of the invention. An additionalembodiment might involve the roller straightening of cylindrical rods,rather than tubular members. Further, by solving Equation (9) andutilizing the one of the two real roots which is more distant from theorigin (x, y, 2 corresponding to a point on the elliptical section 41diametrically opposite to the point 44 shown in FIG. 4, an annularroller may be designed with an internal surface which might be employedin roller straightening a tubular or cylindrical member, e.g., incooperation with a second roller internal to the member. Numerous othermoditications may be made without departing from the invention.

What I claim is:

1. In a method of straightening a length of stock material, which stockmaterial has a cylindrical outer periphery of radius R,,'the steps of:

selectively positioning a set of rollers, each roller having an axiallyvarying radius, the radius R at any point along the roller depending onthe axial distance 2., of the point from the axial center of the rollerin accordance with the formula R= 112 where y is a real rootmtion Ay+By+Cy+Dy+E=O where A cot"0 B 2y,,( cot 0 cotO) C x, /sin 0 +y 4y,, cot 0+y,, cot0 (R cot0)- /sin 0 D (2x ,)/sin 0-2y,, -l-2y cot6 -[(2R y sin0]cot 0 E (x y )/sin 0 y, Rfyf/sinO and where 0 is an acute angle x R1R2 y.7 z /tan0 R is a minimum radius selected for the roller and where 22 hypo-R, 1.

the rollers being positioned to define a path of travel for advancingand straightening the length of stock material with the length of stockmaterial engaging the surface of each roller at the acute angle 0 to theaxis of each roller; and

feeding the length of stock material along said path of travel incontact with the rollers at the acute angle 0 with rotation of therollers and of the length of stock material.

2. In a method as set forth in claim 1, utilizing three pairs ofrollers, said steps of selectively positioning a set of rollers andfeeding the length of stock material comprising:

orienting the rollers of each pair in juxtaposition to one another witheach roller of 'each pair pivoted in an opposite sense away from acentral axis of the pair of rollers at an angle to said central axisequal to said acute angle; while also orienting the pairs of rollerswith two of the pairs of rollers having colinear central axes, and withthe third pair of rollers positioned intermediate the other two pairs ofrollers and having its central axis spaced laterally from the line ofthe central axes of the other two pairs of rollers, a pathinterconnecting the three pairs of rollers along the central axis ofeach pair of rollers constituting said path of travel;

locating the length of stock material running along said path of travelthrough the three pairs of rollers; and

rotatingly driving at least one of the pairs of rollers to feed thelength of stock material along said path of travel through the threepairs of rollers, while rotating the length of stock material, so as tostraighten the length of stock material.

L-566-PT UNITED STATES CERTIFICATE OF CQRRECTION Patent No. 3,780 558Dated i 1 hmmds) P. F. Lilienthal, 1:1 et a1;v

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below: v 5

Title page, column 1, "Karapurath' llemaehandran" should I read--Karapurath Ramachandran--. I f I In the specification, Column 5, line"g Y and 2 should read "X y and z Columzrfijlines' 28 and 29, theequation should read 2 2 t x 2 2 2 .2 i -t R cot 9 --C y My cot 9 y cotG -1- sin 6 Q 9 sin 9 line 36, the equation should read I W 2 2 y y 2y(b a y a Column 7, line #3, the equation should read 2 2 t 0 0 y LP l y2 -l ID sin G sin 9 O K lines 52-56, the equations should read- --c y 4cotge y cot "l sin 9 O O 2,, l sin 6 2 7 2 2x y 3 v 2 cot 6. 0 0 3 2 -1o I D 2y 2y cot 6 a sin 6 '1. 566 PT e UNITED STATES PATENT orflcizCERTIFICATE ()F CORRECTION Patent No. 3 q 7 5'5 Dazed De mp 5: 973

lnvemods) P. F. Lilienthal, II et al. ag 2 It is certified that errorappears in the above-identified parem and that said Letters Patent arehereby corrected as shown below:

E X y y Ll. y r

sin e O sin 9 Column 9, line ll, "moditications" should read---modifications--.

In the claims, Column 9, lines3O-3 L, the equations should read 2 2 LL X2 2 2 2 A R cot --C y Ly cot 9 y cot 6 l 9 sin e O O O sin G 2 2 2 D 22y cot 9 3. 2.19. 1013 9 sin 9 sin 9 2 2 2 2 E 2 n i sin 6 sin 6 Signedand sealed this 22nd day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner ofPatents

1. In a method of straightening a length of stock material, which stockmaterial has a cylindrical outer periphery of radius R1, the steps of:selectively positioning a set of rollers, each roller having an axiallyvarying radius, the radius R at any point along the roller dePending onthe axial distance zo of the point from the axial center of the rollerin accordance with the formula R square root x2 +y2 where y is a realroot of the equation Ay4 + By3 + Cy2 + Dy + E 0 where A cot4 theta B2yo(cot2 theta - cot4 theta ) C xo2/sin2 theta +yo2-4yo2cot2 theta+yo2cot4 theta (R12cot4 theta )/sin2 theta D - (2xo2yo)/sin2 theta-2yo3+2yO3cot2 theta -((2R12yo/sin2 theta )cot2 theta E (xo2yo2)/sin2theta + yo4 - R12yo2/sin2 theta and where theta is an acute angle xoR1 + R2 yo zo/tan theta R2 is a minimum radius selected for the rollerand where
 2. In a method as set forth in claim 1, utilizing three pairsof rollers, said steps of selectively positioning a set of rollers andfeeding the length of stock material comprising: orienting the rollersof each pair in juxtaposition to one another with each roller of eachpair pivoted in an opposite sense away from a central axis of the pairof rollers at an angle to said central axis equal to said acute angle;while also orienting the pairs of rollers with two of the pairs ofrollers having colinear central axes, and with the third pair of rollerspositioned intermediate the other two pairs of rollers and having itscentral axis spaced laterally from the line of the central axes of theother two pairs of rollers, a path interconnecting the three pairs ofrollers along the central axis of each pair of rollers constituting saidpath of travel; locating the length of stock material running along saidpath of travel through the three pairs of rollers; and rotatinglydriving at least one of the pairs of rollers to feed the length of stockmaterial along said path of travel through the three pairs of rollers,while rotating the length of stock material, so as to straighten thelength of stock material.